Nutrition of Salmonoid Fishes

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Abstract
Duplicate groups of 500 chinook salmon (Oncorhynchus tshawytscha) fingerlings raised in water containing 0.2 µg iodine/liter, were fed a low iodide basal ration with added sodium iodide to give 0.1, 0.6, 1.1, 5.1, and 10.1 µg iodide/g dry diet for 24 weeks. A 100-fish sub-lot of each group was fed the diets for an additional 9 months. No significant difference in growth was observed in either feeding period. At the end of the 24-week feeding period the fish fed 0.1 µg iodide had stored significantly less iodine in the thyroid region than had the fish in the remaining groups. At the end of the 9 months' extended feeding the fish fed 0.1 µg iodide had stored significantly less thyroid iodine than had the fish fed 0.6 µg, whereas the latter had stored significantly less than had the fish in the remaining groups. Under the experimental conditions reported, the iodide requirement of chinook salmon fingerlings was 0.6 µg iodide/g dry diet; for advanced parr the requirement increased to 1.1 µg.